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tonearm alignment question

150.148.0.65
Posted on November 3, 2009 at 14:32:02
Lew
Audiophile

Posts: 2686
Location: Bethesda, Maryland
Joined: December 11, 2000
 I mounted my Dynavector DV505 tonearm so as to attain the suggested spindle to pivot distance of 242mm. I then mounted a cartridge using the Turntable Basics mirrored template. For the first time in my life, I found that to make the cartridge align with the TB grids, I had to cant it a bit toward the spindle side with respect to the angle of the headshell. I repeated the procedure two or three times with the same results. Does this have to do with some oddball headshell offset of the DV505 vs the geometry of the TB template, or what? (This is also my first experience with any Dynavector tonearm.) Thanks for any insight. The tonearm/cartridge sounds fine, by the way, but I see a learning experience here.

I misspoke or mis-wrote, posted on November 4, 2009 at 07:06:34
Lew
Audiophile

Posts: 2686
Location: Bethesda, Maryland
Joined: December 11, 2000
 The proper spindle to pivot distance for the DV505 is 226mm, not 242mm as I wrote above. With 15mm stylus overhand, this gives the proper stylus to pivot distance of 241mm. Sorry if I caused any confusion. Not good to rely on one's memory for such data.

The Dynavector tonearm is designed for Stevenson's alignment..., posted on November 3, 2009 at 14:50:37
John Elison
Audiophile

Posts: 10901
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 The Turntable Basics protractor is designed for Löfgren A. Consequently, you will need to move your cartridge forward and turn it inward slightly to achieve Löfgren A. However, Löfgren A is a better alignment, IMO.

Best regards,
John Elison

RE: The Dynavector tonearm is designed for Stevenson's alignment..., posted on November 3, 2009 at 18:55:10
andyr
Audiophile

Posts: 6564
Location: Melbourne
Joined: September 2, 2000
 Hi John,

Given the DV505 has a slotted heashell, what exactly do you mean when you say "the DV505 is designed for a Stevenson alignment"? Surely you just slide the cartridge bolts in the slots until you get it aligned - it doesn't really matter whether it ends up square with the front of the headshell or not?

Incidentally, when I bought my DV505 in about 1989 (traded in on a G2.2 about 6 years ago), the dealer I bought it from made a point of breaking the headshell/arm wand bond and resetting it at a slightly different angle ... he said the DV engineers had got it wrong!! :-)) I guess he was setting it to the Loefgren A angle?

BTW, would there be a different angle for Loefgren B?

Regards,

Andy


RE: The Dynavector tonearm is designed for Stevenson's alignment..., posted on November 3, 2009 at 21:26:18
John Elison
Audiophile

Posts: 10901
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 The slotted headshell has nothing to do with the type of alignment for which a tonearm is designed. The slotted headshell is to allow for variance in stylus-to-mounting-hole distances for different cartridges. The design alignment for the Dynavector tonearm can be found at the Dynavector website in its specification chart.

Effective Length = 241-mm
Overhang - 15-mm
Offset Angle = 21.5-degrees

These parameters define the tonearm's designed geometry. From these numbers you can calculate the null-point alignment.

Inner null-point = 60.1-mm
Outer null-point = 116.6-mm

These null-points represent Stevenson's alignment for an innermost groove radius of 60.1-mm and outermost groove radius of 144.7-mm

In order to achieve Löfgren's A alignment without changing the mounting distance of the tonearm, you need to increase effective length and overhang by moving the cartridge forward in the headshell and you also need to increase the offset angle slightly as shown below.

Effective Length = 243-mm
Overhang - 17-mm
Offset Angle = 22.6-degrees

Sometimes you run into a cartridge with an exceptionally short stylus-to-mounting-hole distance and you can't move it far enough forward in the headshell slots to achieve Löfgren's A alignment. For example, the DL-103 has a rather short stylus-to-mounting-hole distance and sometimes cannot be aligned to Löfgren A in tonearms designed for Stevenson's alignment. On the other hand, most cartridges can probably be moved far enough forward and turned inward slightly to achieve the Löfgren A alignment.

To achieve Löfgren's B alignment all you need to do is move the cartridge forward an additional 0.45-mm beyond that for Löfgren A. The linear offset does not change, but the offset angle decreases ever so slightly.

Best regards,
John Elison

Aah, thanks, John. :-)) nt, posted on November 3, 2009 at 21:28:37
andyr
Audiophile

Posts: 6564
Location: Melbourne
Joined: September 2, 2000
 .


Thanks, John, posted on November 3, 2009 at 16:24:35
Lew
Audiophile

Posts: 2686
Location: Bethesda, Maryland
Joined: December 11, 2000
 I guessed it had to be something like that. With my Triplanar tonearm, the TB protractor tells me to align the cartridge with the headshell, so I assume the Triplanar was designed for Lofgren A.

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